Bengt Sundén

Conjugate mixed convection heat transfer from a vertical rectangular fin

Abstract A numerical investigation of the heat transfer from a rectangular fin by combined forced and natural convection is presented. Results are given for buoyancy parameters in the range of 0 ⩽ Gr/Re 2 ⩽ 2 and convection - conduction parameters in the range of 0 ⩽ √ Re k f L/k s b ⩽ 10 . The results are compared with the conventional fin theory and it is found that concerning the fin efficiency, the latter produces acceptable results although it is not strictly correct.

Numerical and experimental analysis of laminar fluid flow and forced convection heat transfer in a grooved duct

Abstract A numerical and experimental investigation of laminar fluid flow and heat transfer characteristics in a duct with a grooved wall is presented. The plane wall of the duct is kept cold whereas the grooved wall is heated and kept at a uniform temperature. In the experiments, holographic interferometry was applied. The visualized temperature fields were used to reconstruct temperature profiles and from these heat transfer coefficients were evaluated. The governing equations are solved numerically by a finite-volume method for elliptic flows. The results are obtained for Reynolds number ranging from 100 to 1760. The numerically calculated local Nusselt numbers are in good agreement with the obtained experimental values. The streamline plots explain the influence of the fluid flow on the Nusselt number and the pressure drop. The local Nusselt number increases by increasing the Reynolds number. However, the pressure drop penalty was high.

Periodic Laminar Flow and Heat Transfer in a Corrugated Two-dimensional Channel

The laminar convective flow and heat transfer in a two-dimensional corrugated channel with streamwise-periodic variation of the cross-sectional area is investigated numerically. At the channel walls, a uniform heat flux is prescribed. The governing equations are solved by using finite difference approximations. A standard staggered grid is used and the SIMPLE-algorithm is employed in the calculations. Results were obtained for 50 < Re < at Pr = 0.72 and Pr = 5. For fluids like air (Pr = 0.72) a decrease in the heat transfer compared to an uncorrugated channel is found. Only for high-Prandtl number fluids enhancement of the heat transfer is achieved. The pressure drop penalty is high.

Conjugated heat transfer from circular cylinders in low reynolds number flow

Abstract The problem of conjugated heat transfer from a circular cylinder with a heated core region in low Reynolds number flow is considered. The solid may consist of several layers with different thermal conductivities. The energy equations of the fluid and the solid are solved under the conditions of equality in heat flux and temperature at the fluid-solid interface and the solid-solid interfaces. Conditions at infinity are applied for the flow field by Imais asymptotic solution and for the temperature field by a matching to the corresponding asymptotic temperature solution. Results are given for various solid materials and fluids.

The effect of prandtl number on conjugate heat transfer from rectangular fins

Abstract The problem of conjugate heat transfer from rectangular fins is treated numerically. Results are provided for the three Prandtl numbers (three fluids) 0.021, 0.7 and 5.0 and convection - conduction parameters meters in the range of 0 ≤ √Re k f L/k s b = CCP ≤ 5. The results indicated great effects of both CCP and Pr. Comparisons with the simple conventional fin theory show that concerning the fin efficiency, the simple theory yields acceptable results while the temperature variation and local heat flux distributions are not correctly predicted.

Influence of buoyancy forces and thermal conductivity on flow field and heat transfer of circular cylinders at small Reynolds number

Abstract A numeripal investigation of the influence of buoyancy forces and thermal conductivity ratio ( k s /k f ) on the flow field and heat transfer around circular cylinders is presented. The flow field and energy equations are solved under the conditions of continuity in temperature and heat flux at the fluid-solid interface. The buoyancy forces are taken into account by applying Boussinesq’s approximation. Numerical results are given for Reynolds numbers in the range of 5≤ Re ≤40, buoyancy parameters in the range of −1≤ Gr/Re 2 ≤2 and thermal conductivity ratios in the range of 0≤ k s /k f ≤∞.

A theoretical investigation of the effect of freestream turbulence on skin friction and heat transfer for a bluff body

Abstract A theoretical investigation of the effect of freestream turbulence on skin friction and heat transfer around a circular cylinder in cross flow is presented. The flow field is divided into different regions. A two-equation turbulence model together with proper coordinate transformations is used. The calculations are performed for Reynolds numbers in the range of 12500–50000 and turbulence intensities in the range of Tu∞ = 1.25–6.1% and turbulent length scales in the range of Λ f∞ D = 0.1–1.6 . Effect on skin friction and heat transfer of both turbulence intensity and turbulent length scale is found. Good agreement with experiment is achieved.

Transient heat conduction in a composite slab by a time-varying incident heat flux combined with convective and radiative cooling

Abstract Numerical calculations based on finite difference approximations are carried out to assess the thermal response of a composite slab due to a time-varying incident heat flux. The slab, which consists of several layers of various material, is cooled by combined convection and radiation. The slab is rotating and the front and rear surfaces receive the incident heat flux in an alternating fashion. Temperature distributions versus time and space are presented.

Optimizing a refinery using the pinch technology and the mind method

Abstract The Pinch Technology and the MIND method are combined in the analysis of a Swedish refinery. The heat exchanger network of the crude distillation system is analysed using the Pinch Technology. The results show that the steam demand from the boiler units in the energy supply part of the system can be reduced by 20% in the optimized heat exchanger network and by 21% when a heat pump is added to the system. A multi-period cost optimization of the operating strategy is performed using the MIND method. The results from the Pinch analysis are then input to the MIND optimization. The system cost of the total energy system of the refinery is optimized with regard to flexibility in the process system as well as changes of energy costs and the operating conditions of the cogeneration unit. The combination of methods shows that significant capital savings can be achieved when the energy saving potential of the process system is integrated in the overall operating strategy of the energy system. It is, in this case, possible to compare investments in energy saving measures to investments in increased steam production capacity.

Heat transfer and pressure drop in a new type of corrugated channels

Abstract An experimental investigation of heat transfer and pressure drop from a new type of corrugated channels is presented. The investigation has been carried out for Reynolds numbers in the range of 800 Re for one corrugated and one smooth channel. It is found that the heat transfer from the corrugated channel is up to 3.5 times higher than for the smooth one. The pressure drop is however large (5 – 6 times the value of a smooth channel) and it is suggested that the corrugation height and length should be altered in order to balance the increases in heat transfer and pressure drop.